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Profiles of dissolved and particulate 234Th were determined at several stations within the California
Current. Modeling of the disequilibria between the 234Th and 23aU within the surface waters
provides for estimates of the residence time of dissolved thorium with respect to particle scavenging
(TP varies from 6 to 50 days), the particle residence time (TP varies from 2 to 20 days), and the
particulate 234Th flux exiting the surface layer. The model-derived, first-order scavenging rate
constant for dissolved thorium is observed to be proportional to the rate of primary production.
Particle residence times seem to be governed by the rate of zooplankton grazing and the types of
zooplankton present. Model-derived particulate 234Th fluxes are in good agreement with direct
measurements by sediment traps.

White sharks are highly migratory and segregate by sex, age and size. Unlike marine mammals, they neither surface to
breathe nor frequent haul-out sites, hindering generation of abundance data required to estimate population size. A recent
tag-recapture study used photographic identifications of white sharks at two aggregation sites to estimate abundance in
‘‘central California’’ at 219 mature and sub-adult individuals. They concluded this represented approximately one-half of the
total abundance of mature and sub-adult sharks in the entire eastern North Pacific Ocean (ENP). This low estimate
generated great concern within the conservation community, prompting petitions for governmental endangered species
designations. We critically examine that study and find violations of model assumptions that, when considered in total, lead
to population underestimates. We also use a Bayesian mixture model to demonstrate that the inclusion of transient sharks,
characteristic of white shark aggregation sites, would substantially increase abundance estimates for the adults and subadults
in the surveyed sub-population. Using a dataset obtained from the same sampling locations and widely accepted
demographic methodology, our analysis indicates a minimum all-life stages population size of .2000 individuals in the
California subpopulation is required to account for the number and size range of individual sharks observed at the two
sampled sites. Even accounting for methodological and conceptual biases, an extrapolation of these data to estimate the
white shark population size throughout the ENP is inappropriate. The true ENP white shark population size is likely severalfold
greater as both our study and the original published estimate exclude non-aggregating sharks and those that
independently aggregate at other important ENP sites. Accurately estimating the central California and ENP white shark
population size requires methodologies that account for biases introduced by sampling a limited number of sites and that
account for all life history stages across the species’ range of habitats., Downloaded from: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0098078 (8 July 2014).

Although extremely vulnerable to coastal eutrophication, seagrasses represent important structuring elements and sources of primary production in shallow waters. They also generate an optical signature that can be tracked remotely. Accurate knowledge of light absorption and scattering by submerged plant canopies permits the calculation of important plant- and ecosystem-level properties, including rates of photosynthesis, vegetation abundance, and distribution. The objectives of this study were to develop a realistic, yet simply parameterized two-flow model of plane irradiance distribution through a seagrass canopy submerged in an optically active water column, to evaluate its performance against in situ measurements, and to explore the impacts of variations in canopy architecture on irradiance distribution and photosynthesis within the canopy. Allometric functions derived from leaf length-frequency data enabled simple parameterization of canopy architecture. Model predictions of downwelling spectral irradiance distributions in seagrass canopies growing in both oligotrophic and eutrophic waters were within 15% of field measurements. Thus, the model provides a robust tool for investigating photosynthetic performance of seagrass canopies as functions of water quality, depth distribution, canopy architecture, and leaf orientation. Model predictions of upwelling irradiance were less reliable, particularly in the upper half of the canopies. The model was more sensitive to leaf orientation than leaf optical properties, seabed reflectance, or the average cosine of downwelling irradiance. Better knowledge of leaf orientation appears to be a fruitful avenue for improving our understanding of the interaction between seagrasses and the submarine light environment., Cited By (since 1996):36, Seaweeds, CODEN: LIOCA

A standard, universally useful classification scheme for deepwater habitats needs to be established so that descriptions of these habitats can be accurately and efficiently applied among scientific disciplines In recent years many marine benthic habitats in deep water have been described using geophysical and biological data. These descriptions can vary from one investigator to another, which makes it difficult to compare habitats and associated biological assemblages among geographic regions. Using geophysical data collected with a variety of remote sensor systems and in situ biological and geologic observations, we have constructed a classification scheme that can be used in describing marine benthic habitats in deep water., Cited By (since 1996):117, Rocks and Cores, CODEN: OCACD

Concurrent measurements of predator and prey δ15N isotope values demonstrated that a cross-shelf isotopic gradient can propagate through a marine food web from forage species to top-tier predators and indicate foraging areas at a scale of tens of kilometers. We measured δ13C and δ15N in muscle tissues of thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla), and in whole body tissues of walleye pollock (Gadus chalcogrammus) and krill (Thysanoessa spp), sampled across the continental shelf break in the Bering Sea in 2008 and in 2009. We found significant basin-shelf differences at fine scales (<100km) in δ15N among murres but not kittiwakes, and no such differences in δ13C in either seabird species at that scale. We then quantified the multi-trophic signal and spatial structure of a basin-shelf δ15Nitrogen gradient in the central and southern Bering Sea, and used it to contrast foraging patterns of thick-billed murres and kittiwakes on the open ocean. Seabird muscle δ15N values were compared to baselines created from measurements in krill and pollock tissues sampled concurrently throughout the study area. Krill, pollock, and murre tissues from northern, shallow, shelf habitat (<200m) were enriched 1-2‰ in δ15N relative to samples taken from deeper habitats (>200m) to the south and west. Krill δ15N baseline values predicted 35-42% of the variability in murre tissue values. Patterns between kittiwakes and prey were less coherent. The persistence of strong spatial autocorrelation among sample values, and a congruence of geospatial patterns in δ15N among murre and prey tissues, suggest that murres forage repeatedly in specific areas. Murre isotope values showed distinct geospatial stratification, coincident with the spatial distribution of three colonies: St. Paul, St. George, and Bogoslof. This suggests some degree of foraging habitat partitioning among colonies.

Relationships between the surface winds and Acoustic Doppler Current Profiler (ADCP) currents at 20 levels (25 to 329 m) at the western entrance of the Santa Barbara Channel (SBC) at National Data Buoy Center (NDBC) buoy 46054 are evaluated for the 1 year period from 1 June 1996 through 31 May 1997 using a relatively new technique for correlating vectors. Gaps in the data were filled and the resulting time series examined to insure that the statistical properties of the edited data had not been significantly altered. Vertical current profiles, averaged over the year, indicate that the mean signal, although well-defined, is smaller than the variability about the mean. Vertical profiles of current speed and direction suggest the possibility of at least a twolayer system of circulation in the SBC with flow between 25 and 180 m being to the SSW and flow from 260 to 329 m being to the ENE, in agreement with previous results. Because of the existing dynamical balances, the currents are oriented approximately SW/NE, and the direction of the vertical current shear (i.e., the thermal wind) is essentially constant with depth. Thus warmer waters lie to the north and west, and colder waters,
essentially south of the buoy, are consistent with observed cyclonic circulation at the western entrance of the channel. Vector correlations over the entire year indicate that the winds and currents are poorly correlated,

The rock-hosted, oceanic crustal aquifer is one of the largest ecosystems on Earth, yet little is known about its indigenous microorganisms. Here we provide the first phylogenetic and functional description of an active microbial community residing in the cold oxic crustal aquifer. Using subseafloor observatories, we recovered crustal fluids and found that the geochemical composition is similar to bottom seawater, as are cell abundances. However, based on relative abundances and functional potential of key bacterial groups, the crustal fluid microbial community is heterogeneous and markedly distinct from seawater. Potential rates of autotrophy and heterotrophy in the crust exceeded those of seawater, especially at elevated temperatures (25 °C) and deeper in the crust. Together, these results reveal an active, distinct, and diverse bacterial community engaged in both heterotrophy and autotrophy in the oxygenated crustal aquifer, providing key insight into the role of microbial communities in the ubiquitous cold dark subseafloor biosphere., Export Date: 18 March 2016, Article

Field experiments were conducted with oysters, Crassostrea gigas to determine the toxicity of tributyltin (TBT). Oysters were transplanted to over one hundred stations distributed in 25 marinas usually in a transect of four or five stations along a gradient next to vessels extending to station locations distant from vessels. In almost every bay in California there are many vessels, the TBT levels in water are > 50 ng/liter (parts per trillion), and the oysters exhibit a chambering response similar to the chambering response that was indicative of the destruction of the oyster industry in France. Although oysters were transplanted to stations that had extreme environmental conditions (near sewer and petroleum refinery discharges) no evidence of chambering was observed indicating that the chambering response does not occur with every type of environmental stress. In addition, oysters transplanted to a marina that had been abandoned for 18 months did not show a chambering response, whereas those transplanted in marinas that had vessels always showed a chambering response. The use of field techniques in determining toxicity responses worked in this case but the response could have been more clearly defined if more stations were added in each marina and the dose response determined on a marina by marina basis. More TBT measurements in water would have also helped to refine the dose-response relationship. A first estimate of a toxicity value can be determined from these data to be less than 40 ng/liter.

The description of major patterns in beta (. β) diversity is important in order to understand changes in community composition and/or richness at different spatial and temporal scales, and can interrogate processes driving species distribution and community dynamics. Human impacts have pushed many estuarine systems far from their historical baseline of rich, diverse, and productive ecosystems. Despite the ecological and social importance of estuaries, there has not yet been an attempt to investigate patterns of β-diversity and its partitioning along estuarine systems of different continents. We aimed to evaluate if benthic assemblages would show higher turnover than nestedness in tropical than in temperate systems, if well-known impacted estuaries would show greater nestedness than less polluted systems, and to propose a conceptual framework for studying benthic macrofauna beta diversity along estuaries. We analyzed subtidal benthic macrofaunal data from estuaries in Brazil, USA and France. We estimated alpha (. α), beta (. β) and gamma (. γ) diversity for each sampling time in each system, investigated patterns of β -diversity as multivariate dispersion and the partitioning (nestedness and replacement) of β-diversity along each estuary. There was a decrease in the α-diversity along marine to freshwater conditions at most of the estuaries and sampling dates. Beta diversity as multivariate dispersion showed high variability. Most of the estuaries showed a greater proportion of the β-diversity driven by replacement than nestedness. We suggest a conceptual framework for estuaries where relatively pristine estuaries would have their β-diversity mostly driven by replacement while impacted estuaries subjected to several anthropogenic stressors would show total nestedness or total replacement, depending on the stress.

Sediment quality was assessed in San Francisco Bay, California, USA, using a two-tiered approach in which 111 sites were initially screened for sediment toxicity. Sites exhibiting toxicity were then resampled and analyzed for chemical contamination, recurrent toxicity, and, in some cases, benthic community impacts. Resulting data were compared with newly derived threshold values for each of the metrics in a triad-based weight-of-evidence evaluation. Sediment toxicity test results were compared with tolerance limits derived from reference site data, benthic community data were compared with threshold values for a relative benthic index based on the presence and abundance of pollution-tolerant and -sensitive taxa, and concentrations of chemicals and chemical mixtures were compared with sediment quality guideline-based thresholds. A total of 57 sites exceeded threshold values for at least one metric, and each site was categorized based on triad inferences. Nine sites were found to exhibit recurrent sediment toxicity associated with elevated contaminant concentrations, conditions that met program criteria for regulatory attention. Benthic community impacts were also observed at three of these sites, providing triad evidence of pollution-induced degradation. Multi- and univariate correlations indicated that chemical mixtures, heavy metals, chlordanes, and other organic compounds were associated with measured biological impacts in the Bay. Toxicity identification evaluations indicated that metals were responsible for pore-water toxicity to sea urchin larvae at two sites. Gradient studies indicated that the toxicity tests and benthic community metrics employed in the study predictably tracked concentrations of chemical mixtures in Bay sediments., Cited By (since 1996):36, CODEN: ETOCD, Rocks and Cores